If you're refering to a real gopher that lives in a hole in the ground and not a chipmunk, they're easy to get rid of.
Take a hose or a bucket of water and pour it into their hole and flush them out. Then do what you want with them.........
Flushing won’t work. Gopher tunnels have multiple exits. If water comes in one hole, the gophers go out another. You’d have to turn your yard into a swamp for it to work.